Internal combustion engine

ABSTRACT

An internal combustion engine is described which comprises a main combustion chamber and a secondary combustion chamber which is arranged in the cylinder head of the internal combustion engine and is connected via a shot channel to the main combustion chamber. To increase the high-temperature stability, the parts of the secondary combustion chamber which are acted upon by the hot gas jet are made of a material of intermetallic phase.

BACKGROUND OF THE INVENTION

The invention relates to an internal combustion engine comprising a maincombustion chamber and a secondary combustion chamber which is arrangedin a cylinder head of the internal combustion engine and is connectedvia a shot channel to the main combustion chamber.

Compression-ignition internal combustion engines, apart from their maincombustion chamber, often also have a secondary combustion chamber, suchas, for example, a precombustion chamber or a swirl chamber, arranged inthe cylinder head. The ignition of the fuel/air mixture takes place inthis secondary combustion chamber, and the hot gas jet resulting in theprocess passes via a shot channel into the main combustion chamber ofthe internal combustion engine. In addition, when a precombustionchamber is used as a secondary combustion chamber, a deflecting pin isalso arranged in the same, and the secondary combustion chamber, at itsend pointing towards the main combustion chamber, has a burner baseprovided with nozzle openings. Secondary combustion chambers of thistype are normally made of a highly heat-resistant material by means ofwhich the high temperatures occurring there can be coped with. Nimonic80 may be mentioned here as an example of such a material.

A disadvantage of these materials is that they are susceptible tocarbonization, that is, carbides develop and the carbon diffuses intothe metal and cracks it so that it becomes brittle. Damage canconsequently occur at especially stressed points of the secondarycombustion chamber. Thus crack formation, for example, appears at thethin webs between the nozzle openings in the burner base. To avoiddamage of this type, another material must be used. The use of ceramicmaterials is conceivable, but they have the disadvantage that they arenot ductile enough at room temperature; in other words they cannot bereadily processed. Another material is provided by so-calledoxide-dispersion superalloys (ODS), which, however, lose their strengthat very high temperatures and are also expensive.

In the German journal "Nickel-Berichte", Mar. 1960, No. 3, anickel-aluminum alloy of NiAl₃, solid solution is described asparticularly corrosion-resistant at elevated temperatures, whichnickel-aluminum alloy therefore appears as an advantageous material forthe components described in the invention. However, the solid solutionsconcern an Al-alloy having a nickel content of, for example, 3-6% byweight. The atoms occupy static places in the lattice structure duringthe dispersion hardening. The increase, mentioned in the above"Nickel-Berichte", of the high-temperature stability of cast aluminumalloys here relates to the low high-temperature stability of aluminum ingeneral and can raise this, for example, from 200° C. to 300° C.

The materials described in East German Patent Specification 222,930 arealso aluminum alloys of solid solutions having a nickel content of 4-10%by weight, to which the above comments apply accordingly.

The materials described here are thus not suitable for use whereparticular demands are made on the high-temperature stability.

An object of the invention is therefore to make the especially thermallystressed parts of a secondary combustion chamber of an internalcombustion engine from a material which has sufficient high-temperaturestability with adequate ductility for processing at room temperature andlow manufacturing and processing costs.

This object is achieved according to the invention by providing anarrangement wherein at least one of the parts of the secondarycombustion chamber which are acted upon by a hot gas jet are made of thematerial Ni₃ Al intermetallic phase. The parts of a secondary combustionchamber arranged in the cylinder head of an internal combustion engine,which parts are especially thermally stressed, such as the shot-channelburner base provided with openings and extending to the main combustionchamber as well as the deflecting pin arranged in the secondarycombustion chamber, are made of a material of intermetallic phase, suchas, for example, Ni₃ Al or NiAl. The burner base is here made as aseparate part and is subsequently connected, for example welded, to thesecondary combustion chamber.

This material Ni₃ Al intermetallic phase here consists of about 90% byweight of nickel and about 10% by weight of aluminum, which are cast andcooled in such a way that no dispersion takes place, but a compactmaterial having an ordered lattice structure results. In order to obtainadequate ductility at room temperature, small admixtures of othersubstances, such as, for example, 0.02% boron or 0.3% yttrium, can beadded to the material. The comments just made also apply to the materialNiAl, whose basic constituents are present in the stoichiometric ratioof 1:1.

Such materials of intermetallic phase have a high-temperature stabilityin the region of 1000° C., that is, in a region as occurs on highlythermally stressed components of internal combustion engines.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a section through a cylinder of an internal combustionengine having a precombustion chamber in the cylinder head, constructedaccording to preferred embodiments of the present invention.

FIG. 2 is a sectional view of the precombustion chamber of the FIG. 1arrangement.

DETAILED DESCRIPTION OF THE DRAWINGS

An internal combustion engine shown in section and consisting of acylinder block 2 and a cylinder head 3 is designated by 1 in FIG. 1. Thecylinder block 2 contains a piston 4, which is guided in a cylinder andis connected to a crankshaft (not shown here) for the internalcombustion engine 1 via a connecting rod 6 linked to its gudgeon pin 5.A water jacket 7 is also provided. Cylinder block 2, cylinder head 3 andpiston 4 enclose a main combustion chamber in which the actualcombustion takes place. In a known manner, the cylinder head 3 has acamshaft 8 which, via control cams 9 provided on it and bucket tappets10, opens gas-changing valves 11 against the force of their valvesprings 12 and thus permits a gas flow through gas-carrying channels 13.In this arrangement, the cylinder head 3 is closed at the top by acylinder-head cover 14 fixed to it. In addition, the cylinder head 3accommodates a secondary combustion chamber 15 which can be insertedinto it and which--as shown here--can be a precombustion chamber inwhich the combustion process is initiated. Via an injection nozzle 16which is connected to this precombustion chamber 15 and supplied withfuel via a line 17, fuel is injected in a metered manner into thisprecombustion chamber 15 and ignited there. A glow plug 18 is providedas an ignition aid. In addition, this Figure shows the deflecting pin 19inserted in the precombustion chamber 15 as well as the shot channel 20extending from the precombustion chamber 15 to the main combustionchamber.

FIG. 2 is an enlarged representation of the precombustion chamber 15from FIG. 1 in which the injection nozzle and the other components shownin FIG. 1 are omitted for the sake of clarity. Parts identical to theparts shown in FIG. 1 are provided with the same references numerals.Thus the glow plug 18 projecting into the precombustion chamber 15 andthe deflecting pin 19 can be seen. The hot gas jet appearing after theignition strikes this deflecting pin 19 and passes from there throughthe shot channel 20 and the nozzle openings 22 arranged in the burnerbase 21 of the precombustion chamber 15 into the main combustion chamber(not shown here), in which the actual combustion takes place. As caneasily be gathered from the Figure, the deflecting pin 19 and the burnerbase 21 are subjected to high thermal stresses by the hot gas jet. Theso called carbonization, that is, carbide formation with diffusion ofcarbon into the metal of the burner base 21, leads to embrittlement ofthe material with crack formation following therefrom in the burner base21 in the webs 23 located between the nozzle openings 22. For thisreason, the deflecting pin 19 and the burner base 21 are made of amaterial of intermetallic phase which has high-temperature stability.The intermetallic phase Ni₃ Al, which exhibits no carbonizationphenomenon, is resistant to oxidation in air and has a good hot-gascorrosion behavior in the gases appearing during operation of theinternal combustion engine, proves to be suitable here. An increase inthe resistance against corrosion can be achieved by the use of NiAl,which, furthermore, is even lighter. In order to achieve adequateductility of the material at room temperature, which ductility isdesired for the processing, boron can also be added to the material. Inthis way, the components can be manufactured more simply and morecost-effectively. Thus the deflecting pin 19, for example, can beproduced by turning, and the burner base 21 by forging. In addition, theproperties of the material permit good weldability so that the burnerbase 21 can be connected simply and permanently to the precombustionchamber 15 by electron-beam welding or else by brazing. Of course,further elements suitable for optimizing the mechanical properties andthe corrosion behavior, such as, for example, hafnium, manganese, iron,tantalum, zirconium, titanium, cobalt, silicon or niobium, can also beadded to the material.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample, and is not to be taken by way of limitation. The spirit andscope of the present invention are to be limited only by the terms ofthe appended claims.

We claim:
 1. Method of making a secondary combustion chamber for aninternal combustion engine of the type comprising a main combustionchamber and a secondary combustion chamber, the secondary combustionchamber being connected via a shot channel to the main combustionchamber, said method including forming at least one of a burner base ofthe secondary combustion chamber and a deflection pin arranged in thesecondary combustion chamber, which are acted upon in use by a hot gasjet, of the material Ni₃ Al intermetallic phase.
 2. Method according toclaim 1, wherein the burner base is welded to an adjacent structure ofthe secondary combustion chamber.
 3. Internal combustion enginecomprising a main combustion chamber and a secondary combustion chamberwhich is arranged in a cylinder head of the internal combustion engineand is connected via a shot channel to the main combustion chamber,wherein at least one of a burner base of the secondary combustionchamber and a deflecting pin arranged in the secondary combustionchamber, which are acted upon by a hot gas jet, are made of the materialNi₃ Al intermetallic phase.
 4. Internal combustion engine according toclaim 1, wherein a deflecting pin arranged in the secondary combustionchamber is made of the material Ni₃ Al intermetallic phase.
 5. Internalcombustion engine according to claim 1, wherein the burner base iswelded to an adjacent structure of the secondary combustion chamber. 6.Internal combustion engine comprising a main combustion chamber and asecondary combustion chamber which is arranged in the cylinder head ofthe internal combustion engine and is connected via a shot channel tothe main combustion chamber, wherein at least one of a burner base ofthe secondary combustion chamber and a deflecting pin arranged in thesecondary combustion chamber, which are acted upon by a hot gas jet, aremade of the material NiAl intermetallic phase.
 7. Internal combustionengine according to claim 6, wherein a deflecting pin arranged in thesecondary combustion chamber is made of the material NiAl intermetallicphase.
 8. Internal combustion engine according to claim 6, wherein theburner base is welded to the secondary combustion chamber.
 9. Method ofmaking a secondary combustion chamber for an internal combustion engineof the type comprising a main combustion chamber and a secondarycombustion chamber, the secondary combustion chamber being connected viaa shot channel to the main combustion chamber, said method includingforming at least one of a burner base of the secondary combustionchamber and a deflection pin arranged in the secondary combustionchamber, which are acted upon in use by a hot gas jet, of the materialNiAl intermetallic phase.
 10. Method according to claim 9, wherein adeflecting pin arranged in the secondary combustion chamber is made ofthe material NiAl intermetallic phase.
 11. Method according to claim 9,wherein the burner base is welded to the secondary combustion chamber.